How do tanniferous forages influence soil processes in forage cropping systems?

Abstract

Nitrogen‐fixing legumes such as alfalfa (Medicago sativa L.) and sainfoin (Onobrychis viciifolia Scop.) may benefit agricultural systems. In addition to quality forage, both legumes contain secondary metabolites that play important roles in agroecological systems. Alfalfa contains triterpenes (saponins), and sainfoin contains phenolic compounds (tannins). Terpenes and phenolics can influence soil nutrient dynamics by inhibiting microbial activity, which could slow nitrogen mineralization and minimize nitrogen losses. However, research evaluating their influence in the soil has largely come from silviculture or laboratory studies. Therefore, we initiated a field study in Lewiston, UT, assessing how alfalfa and sainfoin influence soil characteristics. The randomized split‐plot block design had three replicates and included a fertilized bale‐and‐remove system, a green manure system (leaving mown plant forage in the field), and a no‐fertilizer bale‐and‐remove system. We measured saponin and condensed tannin (CT) concentrations in alfalfa and sainfoin, respectively, forage biomass, and soil characteristics [e.g., ammonium (NH4), nitrate (NO3), dehydrogenase, organic C, soil respiration, etc.]. Green manure plots showed greater microbial respiration (p = .02), microbial biomass (p < .01), and readily mineralized carbon (p = .04) than other systems. Forage biomass was greater in sainfoin than in alfalfa (p < .001), whereas soil NO3 was greater in alfalfa than in sainfoin (p < .01). The soil NO3 differences could be explained by the inhibition of mineralization by CT in sainfoin compared with the saponins in alfalfa. Planting forages containing tannins may reduce nitrogen losses, thereby enhancing agricultural sustainability.

Influence and distribution of lead nitrate on growth and secondary metabolite accumulation in Withania somnifera (L.) Dunal in vitro shoots

“…The concentrated methanol extract was further used for the phytochemical analysis. Phytochemicals such as flavonoids, phenols and steroids were quantified using the procedure reported by (Kumar et al, 2014;Clemensen et al, 2022).…”

“…The concentration of flavonoids was estimated using the method described by Clemensen et al (2022). The flavonoid content of shoots grown on media supplemented with varying concentrations of lead nitrate is presented in Figure 2.…”

More than a meat- or synthetic nitrogen fertiliser-substitute: a review of legume phytochemicals as drivers of ‘One Health’ via their influence on the functional diversity of soil- and gut-microbes

“…This stage results in these legumes having a higher fiber content ( Capstaff and Miller, 2018 ) and various bioactive phytochemicals, including phenolic compounds (PC), polysaccharides, and phytoestrogens ( Tedeschi et al., 2021 ; Horvat et al., 2022 ). In line with their impact on human health, these compounds have been reported to have positive effects on the health of ruminants’ digestive systems and also contribute to improved soil functions ( Clemensen et al., 2022 ; Mei et al., 2022 ).…”